Getting Arcane spells as a Divine caster.

What are the ways I can go about doing this?
Case in point: I'm thinking of rolling up a Necromancer as a Cleric and doing the full "undead hordes" thing, but I still want to have access to the more fun necro spells, like Magic Jar.

1. Be a Samsaran.

2. Go Oracle and see if the Oracle mystery spells meet your needs.

That's all I got off the top of my head.

Theologian Cleric with the right Domain?
I am not sure if there is a Domain that covers all the neat Undead Spells of arcane casters.

Juju oracle gets magic jar. Also a few other good necromancer spells

A shaman can do it, either with permanent Lore spirit or by using your wandering spirit for Lore.